Most modern internal combustion engines utilize a four stroke operating sequence known as the Otto cycle. The Otto cycle comprises an intake stroke, in which an intake valve opens and a mixture of air and fuel is directed into the cylinder of the engine. A compression stroke then occurs in which the piston compresses the mixture of fuel and air to increase the pressure in the cylinder. A spark provided by a spark plug ignites the mixture just before the piston reaches the top of the cylinder, causing the piston to be forced down the cylinder in the power stroke. An exhaust valve then opens in the exhaust stroke, in which burned gases are forced out of the cylinder. The four strokes are repeated continuously during operation of the engine.
Internal combustion engines operating on the Otto cycle generally utilize spring-loaded poppet valves that selectively open and close the intake and exhaust ports during each cycle. In most engines, a crankshaft is coupled to a timing belt or chain, which in turn is coupled to a camshaft that rotates to open the intake and exhaust valves during the intake and exhaust strokes, respectively. A spring associated with each valve closes the valve during the other cycles.
There are several drawbacks associated with the use of such spring-loaded poppet valves. One drawback is that the valves protrude into the cylinder during each cycle, and there is an inherent risk that the piston may contact an open valve at a high force and cause substantial engine damage. Additionally, valve timing events may be limited due to the protrusion of the valve head into the cylinder.
Another disadvantage with the use of poppet valves in conventional internal combustion engines is that a relatively stiff spring is used to close the valves. Therefore, a relatively strong force is required to overcome the resistive force of the spring to open each valve during each cycle, reducing the efficiency of the engine. Moreover, due to the stiff resistive force provided by the springs, valve timing events may be limited. For example, there generally is a short time period during which both the intake valve and the exhaust valve are open when conventional poppet valves and stiff springs are employed. During this overlap period, unburned hydrocarbon molecules may remain in the combustion chamber for a subsequent cycle, thereby adversely affecting dynamic compression and reducing engine efficiency.
Yet a further disadvantage associated with the use of conventional poppet valves is that energy is lost as a result of an obstruction of the orifice, i.e., because a portion of a poppet valve protrudes through the orifice and into the cylinder. Moreover, flow into the cylinder through the intake port is disrupted when it contacts the head of the poppet valve, i.e., the portion of the valve that seals the orifice in the closed state. The intake valve head may cause turbulence and dead air space within the cylinder, which in turn reduces the efficiency of the engine. Furthermore, when the head of the exhaust valve protrudes into the cylinder during the exhaust stroke, burned gases may not efficiently flow out of the cylinder, which further reduces combustion capabilities.
Various rotational valve designs, which may be used in conjunction with internal combustion engines, have been developed that seek to overcome several of the drawbacks associated with conventional poppet valves. One primary advantage of a rotational valve assembly is the capability to have a substantially unobstructed flow path through a port of a rotating valve. Specifically, because a conventional poppet valve is not employed, and therefore does not obstruct the flow path through an intake or exhaust port, a rotational valve has the potential to significantly increase airflow capability into a cylinder. Moreover, since the stiff spring used in conjunction with conventional poppet valves may be omitted, rotational valve assemblies may achieve reduced mechanical loads.
Previous rotary valve assemblies have included rotating discs, cylinders, sleeves and other spheroidal rotating mechanisms. Such previously known rotational valves rotate a full 360 degrees and are timed such that their apertures overlap with the cylinder during the intake and exhaust strokes. However, due to their 360 degree rotation and continuous motion, such fully rotational valves may experience high temperatures and extreme friction, resulting in high rates of wear imposed on the valve and any related sealing mechanisms.
Moreover, such fully rotational valves generally have fixed aperture sizes, i.e., the size of the aperture in registration with the cylinder may not be varied as the valve rotates. Accordingly, fuel consumption and emissions may be increased by providing a relatively large aperture, particularly during idling conditions.
U.S. Pat. No. 4,944,261 to Coates describes a rotary valve assembly for use in an internal combustion engine. The assembly comprises a two-piece cylinder head that accommodates rotary intake valves and rotary exhaust valves mounted on independent shafts. Each intake valve has two passageways for the introduction and interruption of fuel/air mixture into the cylinder, and each exhaust valve has two passageways for the evacuation and interruption of spent gases from the cylinder.
As the intake valve shaft rotates a full 360 degrees, as driven by a crankshaft, the passageways of the intake valves are selectively placed in registration with the cylinder during intake strokes only. Similarly, the passageways of the exhaust valves are placed in registration with the cylinder during exhaust strokes only. At all other times of rotation, fluid communication is inhibited. By using two passageways on each valve, and by employing independent shafts, the Coates patent states that the valves rotate at a one-quarter speed in relationship to the crankshaft, thereby reducing overall wear on the valves and enabling cooler operating temperatures.
One drawback associated with the rotary valve system described in the Coates patent is that each intake and exhaust valve is fully rotational, i.e., each valve rotates continuously 360 degrees. Accordingly, even though the valves rotate at a one-quarter speed in relationship to the crankshaft, the continuous motion of the valves is still expected to result in relatively high levels of friction, heat and wear.
Moreover, because the valves described in the Coates patent are continuously rotating, the size of the aperture in registration with the cylinder may not be varied. Specifically, while the rotational speed of the valves may be varied in response to the crankshaft rotation, the actual aperture size of the valves remains fixed. It would be advantageous to provide a mechanism configured to vary the aperture size to further improve efficiency at a variety of engine speeds.
Furthermore, while the spherical rotary valve assembly described in the Coates patent may be actuated using a plurality of gears, the assembly does not appear to be easily adaptable for use with other means for actuating, for example, camshafts, solenoids, and other mechanisms. The capability to employ such other means for actuating may afford more design flexibility.
U.S. Pat. No. 6,308,677 to Bohach et al. (Bohach) describes an overhead rotary valve assembly fitted into a cylinder head of an internal combustion engine. The rotary valve comprises diametrical polygonal openings formed therein to bring intake and exhaust ports into and out of alignment with passages leading to and from the combustion chamber. Sprockets that are mechanically driven by the crankshaft are employed to cause the rotary valve assembly to rotate continuously in a 360 degree motion.
The rotary valve system described in the Bohach patent has several drawbacks, many of which are similar to drawbacks described hereinabove with respect to the Coates patent. Specifically, the rotary valve system of the Bohach patent is fully rotational, i.e., rotates continuously 360 degrees. The continuous motion of the valve is expected to result in relatively high levels of friction, heat and wear. Additionally, because the valve described in the Bohach patent is continuously rotating, the size of the aperture in registration with the cylinder may not be varied, as described hereinabove with respect to the Coates patent. Finally, while the rotary valve system described in the Bohach patent is actuated using a plurality of sprockets operatively coupled to the crankshaft, the assembly does not appear to be easily adaptable for use with other means for actuating, such as camshafts, solenoids, etc., which may afford more design flexibility.
Another rotary valve system is described in U.S. Pat. No. 6,293,242 to Kutlucinar. The Kutlucinar patent describes a rotary valve assembly having an elongated valve body mounted in a housing positioned above a head port of an engine. The rotary valve includes an intake port and an exhaust port defined by a valve body, and is arranged for periodic communication with the head port and combustion chamber as the valve rotates. The rotary valve system also includes a secondary intake port for controlling the flow of intake gases into the rotary valve.
The Kutlucinar patent also discloses a sealing system intended to seal the rotary valve in the longitudinal and radial directions. In operation, the sealing elements mounted on the rotary valve dynamically change position depending on the stage of the combustion cycle, for example, the sealing system is configured to form a tighter seal during the combustion stage than during the intake stage.
Additionally, the Kutlucinar patent discloses a throttle control for the rotary valve that has a sliding throttle plate configured to vary the effective size of the intake port opening to compensate for differences in engine speed. The sliding throttle plate may move back and forth in a longitudinal direction within the rotary valve, such that the longitudinal movement of the sliding throttle plate may cover the intake port different amounts at different engine speeds.
The rotary valve system described in the Kutlucinar patent also has several drawbacks, many of which are similar to drawbacks described hereinabove with respect to the Coates and Bohach patents. In particular, the rotary valve system of the Kutlucinar patent is fully rotational, i.e., rotates continuously 360 degrees. The continuous motion of the valve is still expected to result in relatively high levels of friction, heat and wear, despite the fact that a cooling system is employed. Additionally, because the rotary valve system described in the Kutlucinar patent is actuated using a plurality of gears operatively coupled to the crankshaft, like the above-referenced patents, the assembly does not appear to be easily adaptable for use with other means for actuating that may afford more design flexibility.
Another drawback associated with the Kutlucinar patent is the complexity of the sealing system. Specifically, the sealing system employs a significant number of seals, particularly small seals, as depicted in FIG. 6 of that patent. It would be desirable to provide an effective sealing system for a rotary valve that employs significantly fewer components.
In view of these drawbacks of previously known systems, it would be desirable to provide apparatus and methods for a semi-rotating valve assembly that is configured to be easily incorporated into existing internal combustion engine designs.
It also would be desirable to provide apparatus and methods for a semi-rotating valve assembly that improves fuel efficiency relative to known fully rotating valve assemblies.
It further would be desirable to provide apparatus and methods for a semi-rotating valve assembly that reduces the emission of pollutants.
It still further would be desirable to provide apparatus and methods for a semi-rotating valve assembly that improves horsepower and torque.
It still further would be desirable to provide apparatus and methods for a semi-rotating valve body that is configured to rotate less than 360 degrees with respect to a valve housing, thereby reducing friction, heat and wear on the valve body and related sealing components.
It yet further would be desirable to provide apparatus and methods for a semi-rotating valve assembly having an improved sealing assembly configured to effectively seal the valve in radial and longitudinal directions.
It still further would be desirable to provide apparatus and methods for a semi-rotating valve assembly having a means for cooling configured to further reduce valve temperatures and exhaust emissions.
It yet further would be desirable to provide apparatus and methods for a semi-rotating valve assembly that may be actuated using any number of means for actuating to afford more design flexibility.
It still further would be desirable to provide apparatus and methods for a semi-rotating valve assembly that may be used in conjunction with means for varying an aperture size associated with the valve, the means for varying compensating for differences in engine speed to improve engine efficiency and reduce fuel consumption and emissions.